Toughened polar thermoplastics

Abstract

Acrylic impact modifiers for polar thermoplastics such as poly(methyl methacrylate), polyamides, and poly(vinyl chloride) are prepared from emulsion polymer particles with hard methacrylate-rich domains in a continuous polyacrylate network.

We claim: 
     
       1. A toughened blend comprising: (a) 100 parts of poly(vinyl chloride), and   (b) from about 5 to about 80 parts of an impact modifier comprised of at least 50 weight percent of units derived from a C 2  -C 8  alkyl acrylate and of at least 10 weight percent of units derived from a C 1  -C 4  alkyl methacrylate, the impact modifier formed from an assemblage of multi-stage cross-linked emulsion-prepared polymer particles, the first stage being a polymer predominately of units derived from one or more C 2  -C 8  alkyl acrylates and containing at least about 2 weight percent to about 10 weight percent of units derived from a copolymerizable monounsaturated carboxylic acid, the carboxylic acid being at least 40 % neutralized in the form of an ammonium salt at the time of formation of the second stage, and from about 0.2 to about 1.0 weight % of units derived from at least one unsaturated monomer having a plurality of addition polymerizable unsaturated groups, the second-stage polymer being formed in the presence of the first-stage polymer, the second-stage polymer being more than 50% of units derived from methyl methacrylate, the second-stage polymer being formed as cross-linked domains within the first polymer stage, the second-stage polymer being less than about 40 parts by weight of the total stages of the emulsion polymer particle, the second-stage polymer being free of units derived from maleimide or its N-substituted derivatives, and the second-stage polymer containing from about 0.5 to less than about 5 weight percent of units derived from at least one unsaturated monomer having a plurality of addition polymerizable unsaturated groups.   
     
     
       2. The blend of claim 1 wherein the second-stage polymer contains from about 0.5 to about 2.0 weight % of units derived from a unsaturated monomer having a plurality of addition polymerizable unsaturated groups. 
     
     
       3. The blend of claim 1 wherein the impact modifier additionally contains a third-stage polymer, the third-stage polymer containing no units derived from a polyunsaturated monomer having a plurality of addition polymerizable unsaturated groups and containing at least about 90 weight percent of units derived from methyl methacrylate. 
     
     
       4. A molded or extruded article formed from the blend of claim 1. 
     
     
       5. A molded or extruded article formed from the blend of claim 2. 
     
     
       6. A molded or extruded article formed from the blend of claim 3.